Prognostic analysis of acute type A aortic dissection after different surgical interventions: a cohort study

Introduction

Aortic dissection represents an acute course of disease and is most commonly categorized via the Stanford classification, which defines aortic dissection as type A, if the lesion involves the ascending aorta, and type B if the lesion doesn’t involve the ascending aorta (1). Acute type A aortic dissection (ATAAD) is generally defined as the presence of type A aortic dissection occurring within 14 days of onset (2). The annual incidence of ATAAD is approximately 6–30 per 100,000, while the mortality rate ranges from 58% to 62% (1). Moreover, the incidence of type A dissection is likely to be underestimated, as a significant number of patients die before reaching the hospital or being diagnosed. The principle of treatment for type A aortic dissection is to eliminate the primary entry tear, and surgery remains the priority method for the treatment of ATAAD. The surgical procedure is usually selected according to the location of the primary entry tear and the extent of dissection involvement. The ascending aorta and aortic root can be treated with ascending aorta replacement or aortic root replacement (Bentall surgery). For the lesions of the aortic arch and descending aorta, total arch replacement (TAR) plus frozen elephant trunk (FET) stent implantation (the Sun procedure) and partial arch replacement are typically implemented. In some cases, hybrid surgery combined with open surgery and interventional stent implantation can be applied (3). However, the optimal surgical choice for the treatment of type A aortic dissection with regards to the distal extension of the disease remains controversial.

We thus compared the prognosis of patients who underwent the Sun procedure with that of those who were not treated with the Sun procedure, with both groups having similar preoperative conditions. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2048/rc).

Methods

Patients

The data of all patients with ATAAD admitted to Beijing Anzhen Hospital from August 1, 2020, to August 16, 2022, were collected. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The Ethics Committee of Beijing Anzhen Hospital of Capital Medical University approved this retrospective study (No. 2024246x). The requirement for individual consent was waived due to the retrospective nature of the analysis. In this study, 452 patients were included, including 344 patients who received the Sun procedure and 108 patients who did not, irrespective of the surgical technique concerning the proximal part of the aorta including either a Bentall procedure or a tube graft prosthesis replacing the ascending aorta. Those who did not receive surgical treatment and those whose interval between operation and onset of dissection was more than 14 days were excluded.

Definitions

For this study, cardiogenic shock was defined as systolic blood pressure ≤90 mmHg, cardiac index ≤2.0 L/min/m², or the need for intravenous inotropic drugs. Pneumonia was defined as fever or elevated white blood cell count in patients with inflammatory infiltration on chest radiography or lung computed tomography (CT). Respiratory failure was defined as a blood gas oxygen partial pressure ≤60 mmHg or an oxygenation index ≤300 mmHg. Sepsis was defined as fever or elevated white blood cell count with a positive blood culture. Prolonged mechanical ventilation (PMV) was defined as a postoperative mechanical ventilation time ≥48 hours. Malperfusion syndrome (MPS) for all organs was defined as preoperative aortic CT angiography (CTA) showing the involvement of the corresponding vessels by dissection with the following concomitant symptoms: cerebral MPS (stroke symptoms in the corresponding vascular area with positive head CT findings), spinal MPS (paraplegia), limb MPS (corresponding to sensory or motor deficits or loss of pulse in the limb), renal MPS (serum creatinine ≥442 µmoI/L, oliguria, or both), mesenteric MPS (abdominal pain, abdominal tenderness, or gastrointestinal bleeding), and myocardial MPS (myocardial infarction in the corresponding area with elevated troponin). Distal aortic events (DAEs) were defined as postoperative distal aortic dilation ≥50 mm in diameter or ≥10 mm/y in velocity, with or without surgical intervention (4,5).

Surgical indications and techniques

Patients in the Sun procedure group received proximal treatment and the Sun procedure; the specific details of the Sun procedure have been in previous studies from our center (6,7). The non-Sun procedure group received proximal treatment with or without partial arch replacement. The principle of surgical treatment for ATAAD was to eliminate the primary entry tear. The Sun procedure was considered for patients with the following conditions: (I) aortic arch dilation; (II) severe dissection of brachiocephalic artery; (III) complication with Marfan syndrome; (IV) a primary entry tear located at the aortic arch; and (V) younger age and good physical condition. The operation included proximal treatment, arch treatment, and distal treatment. In this study, patients underwent proximal management including simple ascending aorta replacement, aortic root replacement (Bentall surgery), and David surgery. Aortic valve replacement was considered when any of the following occurred: (I) patients with moderate or severe aortic regurgitation indicated by preoperative echocardiography; (II) patients with large aortic root aneurysm; (III) patients with severe damage on the sinus canal junction that made it difficult to proximal anastomosis when performing ascending aorta replacement. The treatment of the arch included partial arch replacement (the distal end of the artificial vessel replacement was located at the proximal end of the left common carotid artery opening, without replacing the brachiocephalic arteries) and TAR. The distal treatment method is FET technique. Right axillary artery intubation or innominate artery intubation was used for unilateral selective cerebral perfusion. For those who have not used the right axillary artery or the innominate artery as the inflow site for cardiopulmonary bypass (CPB) for various reasons, a left common carotid artery cannulation would be chosen to perform unilateral selective cerebral perfusion. In individual preoperative cases where there were evidences of higher risks of brain complications, left common carotid artery intubation was performed in conjunction with the right axillary artery or innominate artery cannula for bilateral selective brain perfusion. The flow rate of cerebral perfusion was 5 mL/kg/min.

Clinical and imaging follow-up

Follow-up began immediately after the operation. Follow-up information included postoperative all-cause death and its causes, secondary aortic surgery, and postoperative aortic CT. Aortic CT review was performed at discharge; at 3 months, 6 months, and 1 year after surgery; and annually thereafter. According to the partitioning method proposed by Fillinger et al., the aorta was divided into 11 zones (8). The maximum diameter (mm) was measured from the axial plane of the outer wall of the aorta in each zone, and the maximum aortic diameter among all zones was recorded. The aortic dilation rate (mm/y) was calculated by dividing the difference between the diameter of the last CT and that of the first CT by an interval of more than 6 months.

Statistical analysis

Data processing and analysis were performed using SPSS 26 (IBM Corp., Armonk, NY, USA) for Windows and R version 4.4.0 (2024-04-24; The R Foundation for Statistical Computing). Since the number of cases included in each group of this study was more than 30, the continuous variables were treated according to a normal distribution and are expressed as the mean ± standard deviation. The t-test was used to analyze continuous variables, while the chi-square test was used for categorical variables. The nearest matching method was used for PSM, and the caliper value was set to 0.1. The Sun procedure group was used as the experimental group, and the non-Sun procedure group was used as the control group in 1:3 matching. Preoperative factors that could potentially affect prognosis as determined by clinical experience were included in the matching. Common baseline data and preoperative factors that may affect postoperative prognosis reported by clinicians in our center and previous literature were comprehensively referred to as variables for PSM. The Kaplan-Meier (K-M) method was used to analyze postoperative midterm survival and DAEs, and the log-rank test was used to compare the results between groups. Risk factors for postoperative midterm death and DAEs were analyzed via Cox regression. Due to the possible competition between postoperative death and DAEs, sensitivity analysis of DAEs was performed using Fine-Gray analysis. Risk factors for postoperative 30-day death were analyzed by logistic regression. The variables included in the multivariate regression analysis were selected with comprehensive reference to the results of univariate analysis, clinical experience and previous literature reports. With the exception of Marfan syndrome, all variables included in the regression analysis were intraoperative or postoperative factors. P<0.05 was considered statistically significant. All data produced in the study are provided in the article.

Results

PSM analysis

A total of 300 patients were included after propensity score matching (PSM) between the two groups was completed, with 207 patients in the Sun procedure group and 93 patients in the non-Sun procedure group. The groups were well balanced, as shown in Table 1 and Figure 1. The results of PSM are shown in Table 1. Intraoperative data and postoperative complications after matching are shown in Tables 2,3, respectively. The comparison of postoperative results after PSM is shown in Table 3. The incidence of postoperative spinal MPS in the Sun procedure group was higher than that in the non-Sun procedure group (P=0.003).

Figure 1 Absolute mean differences before and after PSM. BSA, body surface area; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; MPS, malperfusion syndrome; NYHA, New York Heart Association; PSM, propensity score matching.

Analysis of postoperative 30-day death

A total of 26 deaths occurred in the Sun procedure group while 5 occurred in the non-Sun procedure group at the point of 30-day after the operation. The postoperative 30-day mortality rates were 12.56% and 5.38% in the Sun procedure group and the non-Sun procedure group after PSM, respectively (P=0.06) (Table 3). Although there was no statistical difference in postoperative 30-day mortality rates between the two groups, Sun procedure group did have a higher death rate than the other group. Multivariate logistic regression (Table 4) showed that the risk factors for postoperative 30-day death were postoperative cardiogenic shock [odds ratio (OR) =5.16, 95% confidence interval (CI): 1.16–22.95; P=0.03], postoperative cerebral MPS (OR =7.01, 95% CI: 2.57–19.08; P<0.001), postoperative spinal MPS (OR =4.35, 95% CI: 1.20–15.81; P=0.03), and need for CRRT (OR =8.09, 95% CI: 3.05–21.45; P<0.001). According to Table 3, although there was no significant difference, the probability of postoperative cardiogenic shock and need for CRRT was slightly higher in Sun procedure group. While the incidence of postoperative cerebral MPS was very similar between the two groups.

Analysis of postoperative midterm death

At the end of follow-up, a total of 31 deaths occurred in the Sun procedure group while 8 occurred in the non-Sun procedure group. A K-M analysis was performed for postoperative death, as shown in Figure 2. The 3-year survival rates were 85.02% (95% CI: 80.30–90.03%) and 91.40% (95% CI: 85.87–97.28%) in the Sun procedure group and the non-Sun procedure group after PSM, respectively (P=0.12) (Tables 5,6). Multivariate Cox regression (Table 7) showed that the risk factors for postoperative death were postoperative cardiogenic shock [hazard ratio (HR) =2.98, 95% CI: 1.29–6.92; P=0.01], postoperative cerebral MPS (HR =5.34, 95% CI: 2.56–11.16; P<0.001), postoperative spinal MPS (HR =2.82, 95% CI: 1.11–7.16; P=0.03), and need for CRRT (HR =4.55, 95% CI: 2.22–9.32; P<0.001).

Figure 2 Kaplan-Meier survival analysis.

Analysis of postoperative DAEs

At the end point of follow-up, five DAEs occurred in the Sun procedure group while eight occurred in the non-Sun procedure group. K-M analysis was performed for postoperative DAEs, as shown in the Figure 3. At 3-year follow-up, the probability of no DAEs occurring was 97.17% (95% CI: 94.76–99.65%) and 91.59% (95% CI: 85.80–97.78%) (P=0.02) in the Sun procedure group and non-Sun procedure group, respectively, representing a significant difference (Tables 8,9). Multivariate Cox regression (Table 10) showed that the risk factors for DAE were Marfan syndrome (HR =20.36, 95% CI: 5.51–75.20; P<0.001) and non-Sun procedure (HR =3.42, 95% CI: 1.11–10.56; P=0.03). Considering the possibility of competition between death and DAEs, we proceeded the Fine-Gray analysis (Table 11), and the results were similar to those of cox regression, which showed that the risk factors for DAEs were Marfan syndrome (HR =19.02, 95% CI: 4.40–82.23; P<0.001) and non-Sun procedure (HR =3.38, 95% CI: 1.04–11.02; P=0.04).

Figure 3 Kaplan-Meier DAE-free analysis. DAE, distal aortic event.

Discussion

This study shows that the Sun procedure is a feasible option in many patients with ATAAD. The Sun procedure is generally considered to have better long-term treatment effect for ATAAD because it can rapidly dilate the true lumen, activate positive vascular remodeling, provide early restoration of blood perfusion to the affected organs, and reduce the risk of secondary surgical intervention (9). However, the Sun procedure poses certain perils to patients, such as greater surgical risk, especially in the elderly patients with organ malperfusion (10), and thus is generally recommended to be performed in a surgical center with experienced specialists (11). A meta-analysis of 7,967 cases of the Sun procedure (12) indicated that the incidence of postoperative cerebrovascular complications, paraplegia, renal failure, and in-hospital mortality were 7.104%, 3.465%, 14.969%, and 8.933%, respectively. In contrast, simultaneous simple ascending aorta replacement, aortic root replacement, and partial arch replacement, provides a shorter operation time and less trauma and thus has been considered more suitable for older adult or frail patients who cannot tolerate the Sun procedure (13). In our study, after we obtained cases with similar preoperative conditions using PSM, the incidence of postoperative complications in the Sun procedure group, except for that of postoperative spinal MPS, was not found to be significantly different from that in the non-Sun procedure group. Although there was no statistical difference, postoperative 30-day mortality was higher in Sun procedure group than that in the other group. This discrepancy may be due to the difference in population selection of different studies and the improvement of surgical techniques in our center in recent years.

With regard to risk factors associated with postoperative 30-day death, the incidence of postoperative cardiogenic shock and need for CRRT remained higher in the Sun procedure group, although there was no significant difference. This may indicate that compared with simple proximal operation, Sun’s procedure is more likely to cause potential myocardial and renal injury, resulting in slightly higher early postoperative mortality. There was little difference in the incidence of postoperative cerebral MPS between the two groups. This indicates that under reasonable cerebral protection measures (deep hypothermia circulatory arrest and selective cerebral perfusion), there is no difference in the risk of cerebral MPS between Sun’s procedure and simple proximal surgery.

Takagi et al. (14) compared the prognosis of patients who underwent simple ascending aorta replacement and TAR + FET surgery and found that there was no significant difference in early and middle postoperative mortality between the two groups, while the incidence of postoperative aortic events was higher in the simple ascending aorta replacement group, which was similar to the conclusion reached in our study. Omura et al. (15) also reported that TAR + FET surgery may provide a better long-term prognosis. The study by Biancari et al. (16), however, arrived at an opposite conclusion after comparing the prognosis of patients who underwent type A aortic dissection repair, which may be due to the fact that the study population was European and younger than 60 years old. Many studies have shown that advanced age is a risk factor for poor prognosis after type A dissection (17,18). Therefore, simple proximal surgery should be considered for older adult patients. Some studies have suggested that the 5-year survival rate after type A dissection may range from 70% to 80%, and about 12% to 24% of late deaths may due to distal aneurysm rupture (19-21). Moreover, patients who undergo non-TAR surgery have a higher incidence of postoperative DAEs (21,22). In this study, the average age of all patients was 49.46±11.67 years, and the average age after PSM was 50.72±11.73 years. Thus, there exists a difference of more than 15 years between the onset age and the life expectancy of the population. The age of onset of aortic dissection is generally young, which is associated with poor control of hypertension. Since most of the patients admitted to our center were brought in by ambulance, most of these patients were treated with antihypertensive drugs on the way to the emergency department of our center, so the preoperative blood pressure was close to normal.

In this study, PSM was used to control preoperative confounders. Multivariate logistic regression and multivariate cox regression were used to analyze the risk factors related to postoperative death and DAEs. Fine-Gray analysis was used for sensitivity analysis, thus the conclusion was relatively reliable. However, because the variables included in the regression were selected based on clinical experience and results reported in previous studies (19,23,24), there may be some bias.

Marfan syndrome is currently a recognized high-risk factor for aortic dissection, which causes the degeneration of the medial aortic wall, leading to a high incidence of dissection and aneurysm (19). In our study, patients with type A aortic dissection combined with Marfan syndrome had a higher incidence of postoperative long-term events. There were seven patients with Marfan syndrome after PSM, two of whom died before the occurrence of aortic events, and three of the remaining five experienced DAEs. Rylski et al. (25) found that for patients with type A aortic dissection complicated with Marfan syndrome, a primary surgical replacement range not reaching the aortic arch may lead to poor prognosis. The indications for reintervention after first-stage dissection repair in Marfan syndrome patients are also more stringent than are those in the general population, and the Sun procedure is more likely to be selected in first-stage surgery to obtain a better long-term prognosis. The study of Chen et al. (26) showed that the Sun procedure had a relatively obvious effect on postoperative positive remodeling of the aorta in patients with ATAAD complicated with Marfan syndrome. Overall, although the postoperative 30-day and midterm mortality was slightly higher in the Sun procedure group which might due to the possibility for Sun’s procedure causing a relatively high incidence of postoperative spinal MPS, there was no significant difference between patients treated with the Sun procedure and those treated with other operations involving only proximal and partial arch treatment, but the Sun procedure can achieve a lower long-term reintervention rate. Therefore, for patients with Marfan syndrome, younger patients, and most patients who can tolerate it, the Sun procedure with a wider range of operations should optimally be considered as the first-stage of treatment. On the other hand, the higher incidence of spinal MPS after the Sun procedure is concerning. In our study, 19 patients developed paraplegia after the Sun procedure, 7 of whom died during hospitalization. Among the 12 survivors, 3 had the paraplegia symptoms basically disappear at the time of discharge, and 5 had symptoms improved to varying degrees during follow-up. Based on our previous experience, the reason for Sun procedure increasing the risk of paraplegia depends more on the number and condition of the patient’s intercostal artery opening into the false lumen. Because the insertion of the elephant trunk stent can cause rapid closure and intraluminal thrombosis of the false lumen, this can lead to acute interruption of blood flow in the intercostal artery opening in the false lumen, resulting in acute spinal ischemia. In fact, the largest vessel that supplies blood to the spinal cord is the Adamkiewicz artery (27). The length of the trunk stent is far from reaching the level of the Adamkiewicz artery, so in most patients, Sun procedure is safe. Also, there is study has shown that residual tear at the distal end of elephant stent is also one of the risk factors for paraplegia. Therefore, more adequate and timely preoperative and postoperative aortic CTA assessment may reduce the incidence of paraplegia after Sun procedure (28). For patients with a high proportion of the intercostal artery located in the false lumen preoperatively, patients with severe Adamkiewicz arteries dissection, and patients with naturally thin Adamkiewicz arteries, it may be necessary to consider avoiding Sun procedure or using a shorter elephant trunk stent.

Study limitations

The follow-up time of this study was relatively short, and the long-term prognosis may not have been accurately described and compared. Assessment of life quality during follow-up was inadequate. The involvement of the proximal part of the aorta including the surgical decision may have had an impact on the outcome after surgery for ATAAD. A large-sample, multicenter study is warranted.

Conclusions

This retrospective study shows that the Sun procedure is a suitable option for many patients with ATAAD.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2048/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2048/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2048/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2048/coif). A.M. serves as Editor for EJCTS, Secretary General for SATS, and a member for AATS, EACTS, ST, TT and SATS. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The Ethics Committee of Beijing Anzhen Hospital of Capital Medical University approved this retrospective study (No: 2024246x). The requirement for individual consent was waived due to the retrospective nature of the analysis.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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(English Language Editor: J. Gray)